The Spring 2025 Iberian/Spanish Power Outage

What Happened to Spain's Electricity on Monday 28th April 2025?

From 12:30 pm on Monday 28th April 2025, power was lost to domestic and business customers as well as city infrastructure and all train services across the whole of Spain. The power outage also affected Portugal, Andorra and a small part of southern France. This was a mass power outage that affecting the whole Iberian Peninsula, lasting approximately 8 hours.

Catalonia's Civil Protection Service announced that, by Monday 28th April, 11.00 pm, at least 63% of Catalonia, around 3,000 megawatts, had recovered its electricity. By Tuesday morning Electricity was fully restored.

The Building blocks of the Spanish Electrical Grid

Power generation in Spain is provided by nuclear, Wind, solar and some carbon burning power stations. Distribution of nationwide power from the generation source to the city substations is handled by a single company called Red Eléctrica de España (REE). REE also maintains bi-directional interconnects with France and Portugal to balance the load in times of demand taking electricity from France and in times of surplus, providing electricity to France Portugal and Andorra. REE also has interconnects to the Beleric Islands.

At a regional and local level there are electricity companies, such as fecsa-Endesa in Catalonia, that distribute the electricity from the national grid to local voltage step down transformers and provide the local connection between the user’s electricity metre and the substation. Regional Electricity companies like Fecsa-Endesa also own and maintain power generation sites, such as the Besós Municipal Rubbish furnace, and feed this power into the REE grid.

The Electricity network, like any other network is built on a hieratical structure with the REE grid being the top tier followed by regional electricity companies, Balancing the load and maintaining a stable frequency of 50 Hz is essential across the whole electricity network because if the frequency drops below 47.5Hz then large transformers begin to trip out causing power outage. As electrical demand (load) increases, the frequency drifts down so more generation capacity has to be put onto the grid to maintain the frequency at 50 Hz. Load balancing and switching in electricity generation capacity is the responsability of REE.

Traditional media reports of widespread chaos

Most English language media is reporting rubbish designed to sensationalise.

Most business sent employees home after a couple of hours when it became obvious that the power was not going to be restored quickly. Shops and supermarkets closed early. Restaurants closed and bars were serving cold food and drinks only. I went out at around 6 pm to try and find a hot dinner, and was surprised to see all restaurants closed or not serving hot food. I walked through two neighbourhoods thinking it was a zonal transformer or main power cable severed by building works. On the street it was clear that no one knew the scope of the outage because Cell phone towers (that have 4 hours of battery redundancy), fibre internet, television and all other media was out. The police were on the streets marshalling road traffic.

I walked as far as Sants, the main railway station, in Barcelona thinking it would have generator backup and was informed by security that the train circulation was suspended, and that the station was closed due to a nationwide power outage which at the time did did not fully believe. Walking in the streets along with everyone else, there was no panic or looting, most people were sitting in terrace bars drinking not so cold beer and eating cold tapas. Some small shops were open, only accepting cash and I bought snacks.

Cash machines and contactless payment (requires internet and power), like everything, else were not working and Spain is pretty much a cashless society nowadays with most people using contactless cards and only carrying enough cash to buy a cheap meal (10-20 euros!) reports of mass panic buying are false because people simply do not carry the cash needed for this. People were just buying cold food for the evening meal in the small shops that were open.

Busses were still running and overcrowded because the metro and commuter rail networks were suspended. People were stranded by the closure of national rail so Sants Station remained open to stranded passengers overnight so that passengers could sleep on the floor. Trains were restored around 11:00 pm so some stranded passengers were able to get home or to their destination albeit very late and hungry. Some passengers were also able to get busses which were running with a reinforced service. Domestic power was restored after the trains and civic infrastructure, at around midnight in Barcelona city.

The weather on Monday the 29th of April was a sunny spring day at about 19 to 20 degrees celcius in Barcelona. The temperature was not too high to need air conditioning nor too low to need heating (increased electrical load). There were no sporting events of national significance such as the football world cup which increases load as everyone is watching TV at the same time.

An unintentional media blackout was caused by the loss of cellular phone networks, tv, and internet, which was probably a benefit to the national government because no one knew what was going on so there was not widespread panic nor looting nor any collapse of civic society. However, it is said that any society is only 24 hours away from total collapse, so the restoration of power at midnight was timely.

Unknown root cause?

Official Spanish Government statement:

Monday 28th of April 6 pm: "We do not rule out any hypothesis" Spanish Prime Minister Pedro Sánchez, in his mid-afternoon speech, said that "we do not have conclusive information on the causes of the blackout and that the government does not rule out any hypothesis".

False - Initial Portuguese reports of Atmospheric Phenomenon:

Monday 28th April: Online sources are claiming that the Portuguese operator REN (Redes Energéticas Nacionais), claimed that the power outages in Portugal were the result of a failure in the Spanish grid, related to a rare atmospheric phenomenon where extreme temperature variations induce oscillations on very high voltage lines (400 kV). However, REN strongly denied these reports.

Monday 28th April 11:30pm: The Portuguese electricity operator REN said all substations were fully operational and the national network had been “perfectly stabilised” by 11.30pm on Monday 29th of April.

False - French Electrical Grid Failure or French Interconnect failure:

Monday 28th April: French grid operator RTE, denied that the power blackout in Spain and Portugal on Monday was due to a fire on a line between the cities of Narbonne and Perpignan.

False - Atmospheric Phenomenon:

Tuesday 29th April: Spain’s national meteorological office, AEMET, ruled out the weather as a possible culprit. "During the day of 28 April, no unusual meteorological or atmospheric phenomena were detected, and nor sudden variations in the temperature in our network of meteorological stations."

False - Insufficient Spanish Nuclear Power Generation Capacity:

Tuesday 29th April: Pedro Sánchez rejected the notion that the blackout was caused by a lack of sufficient nuclear power. Nuclear power plants have not yet fully recovered their activity and were running on diesel generators to ensure cooling water flow for the reactors. The five nuclear power plants in Spain have a combined installed capacity of 7.4 GW and at 12:30 pm on Monday were supplying 3.388 GW (10% of national demand). For context the drop of supply was 15 GW across the Spanish grid at 12:33 on Monday 28th April.

Very unlikely - Cyber-attack:

Tuesday 29th April: Judge José Luis Calama of the Audiencia Nacional, Spain's central criminal court, is opening an investigation into whether the power outage "could have been an act of cyber-sabotage against Spanish critical infrastructure." Which would fit within the parameters of a terrorist crime and therefore within the juridiction of the Audiencia. The judge requires the National Cryptology Centre and the Red Eléctrica de España (REE) to prepare reports within 10 days.

The National Cryptology Centre, which operates under the National Intelligence Center (CNI), has limited itself to saying that it is investigating the cyberattack hypothesis. Spain has become one of the countries most targeted by cyber-attacks considered critical due to their severity, with several hundred each year. The Joint Cyber Command, which is under the Ministry of Defence, is also investigating the possible cyber origin of the blackout.

The preparation and execution of a cyberattack that shuts down the electricity of almost two entire countries is very complex requiring a coordinated operation that knocks out multiple electricity network nodes simultaneously so "A blackout of this scale through a cyberattack would be complicated because of the segmented electrical networks. An attack, for example, could target transformers or substations, causing damage to hardware until it starts to fail. But coordinating such a large and synchronized attack would be extremely difficult."

The only successful cyber-attacks of this scale to an electricity network took place in Ukraine in 2015 and 2016, with Russia being the culprit.

Red Eléctrica de España (REE) statement:

Tuesday 29th April: The blackout was not the result of a targeted (cyber) attack with "no evidence of any kind of intrusion into the Red Eléctrica control system. Two consecutive events, which took place at 12.32pm on Monday and then a second and a half later, pointed to a generation disconnection" (transformers tripping because of a drop in frequency) that had cut off the supply across the peninsula. "While the system absorbed the hit of the first event, it could not cope with the second." supply throughout the peninsula fell from 26.695 to 15.970 megawatts and the grid was unable to support the load causing widespread disconnection of power generation.

By Tuesday morning, all of Spain’s electricity substations were up and running, and 99.95% of the country’s power supply had been restored.

Probable - Claims green energy to blame for blackouts:

Spain is one of the European nations with the highest amount of wind and solar energy production. The downside is that wind and solar are dependant on the weather and on Monday 28h of April, it was a sunny spring day with no noticeable drop in wind. Traditional energy sources such as coal, gas and nuclear provide inertia from enormous spinning turbines which can stabilise the grid frequency. Wind and solar do not have the same enourmous machinery that provides this inertia. At 12:30 pm wind was supplying 3.643 GW (10.68% of demand) and at 12:35 pm wind was supplying 2.290 GW.

Looking at the energy supply graphs from REE, I see that Solar panels (solar fotovoltaíca) was supplying 18.068 GW (53.34% of demand) at 12:30 pm and at 12:35pm Solar panels were providing only 6.778 GW. So about 11 GW of solar power suddenly disappeared from the grid, yet the weather and sun remained constant.

Tuesday 29th April: REE’s head of services, Eduardo Prieto, said preliminary investigations show "the problem had originated in south-west Spain", which is where much of the country's solar energy is generated. The region of Castile and León produces up to 1.436 GW and the region of Extremadura 5.347 GW (2022 figures) of solar panel power. Typically, a solar panel farm in Spain produces anywhere up to 500 MW so no one solar panel farm failure could have caused the 11 GW drop in supply which again points back to Red Eléctrica de España (REE) and their distribution grid.

Conclusions

After living in Catalonia for 20 years, I have seen some large power outages sometimes affecting half the city of barcelona and lasting a few hours but a power outage across the whole of Spain is unprecedented. Hopefully, the root cause will not get politically buried, even if people stop talking about this. Why did Spain’s solar panel energy disappear from the grid suddenly (11 GW drop in under 5 minutes) on the 28th April 2025?

What is clear is that the responsibility and blame falls to Red Eléctrica de España (REE). A cyber-attack, although no evidence as yet has been identified, is not completely ruled out. External factors such as weather or interconnects with France or Portugal are not to blame, In fact, at the time of the incident Spain was exporting electricity to Portugal, France and Morrocco.

I think that the root cause will come down to a lack of investment by REE in the infrastructure that switches in electrical supply to the grid to cope with falling and rising demand, probably down to not modifying the infrastructure sufficiently to cope with the differences and challenges of supply from renewables such as wind and solar.

Another theory that I have not seen reported anywhere could be simple human error. REE has a network operations centre constantly monitoring supply vs demand every second and adjusting the network according to parameters such as predicted demand, actual demand, actual supply and available/reserve supply. A NOC operator may not have switched in enough supply or a computer model of predicted demand vs supply could have been interpreted incorrectly.